1. Field of the Invention
The present invention is broadly concerned with improved spreader apparatus designed for use in square or rectangular inlet decks forming a part of pellet dryers or coolers, in order to evenly spread product to a desired depth on the deck. More particularly, the invention pertains to such spreader apparatus and complete dryer/cooler inlet decks, wherein use is made of spreader including a plurality of elongated delivery tubes driven in unison across the deck for distribution of product thereon. In alternate embodiments, a rotating spout distributor is used to spread product on a conveyor belt or the like.
2. Description of the Prior Art
It is a common requirement in numerous bulk material processes to dry and/or cool a product at some intermediate or final stage of production. For example, in extrusion processing of animal feeds or the like, the extrudate emerges from the extruder at an elevated temperature and at relatively high moisture levels. In order to more readily handle the product and to assure its shelf life, it is generally necessary to dry and cool the extrudate to room temperature and moisture levels of perhaps 8-12% by weight.
In many extrusion systems therefore, dryer/cooler apparatus is provided downstream of the extruder so that the extrudate is dried and cooled on a continuous basis. A variety of different dryers or coolers have been used in this context, for example vertical dryers or other types of upright dryers with continuous air flow therethrough. Such dryers have a square or rectangular inlet stage or deck where incoming product is received. In order to achieve the best and most efficient drying/cooling results, it is important that the incoming product be evenly spread over the inlet deck. If not, the product may be unevenly dried or cooled during passage through the dryer/cooler.
A number of expedients have been used in the past in an attempt to evenly spread incoming pelleted or similar products across the square or rectangular inlet decks. A common approach is to simply dump product onto the deck using a rotating spout and then make use of a rotatable rake to spread and even the product. The problem with rakes is that they cannot spread product in the corners of the deck. Thus, while the central region of the deck described by rake rotation is evenly spread, the product in the corners will either be at a level higher or lower than the central region.
Another approach is described in U.S. Pat. Nos. 5,909,943 and 6,029,366. These patents make use of an oscillating inlet spreader including an elongated delivery spout which is driven through a range of motion in an effort to evenly spread pellets across a dryer/cooler deck. A specialized outlet grate is also provided with the spreader in a further effort to uniformly spread product. Level detectors and a variable frequency drive are also used. Consequently, spreaders as disclosed in these references are excessively complex and costly.
There is accordingly a real and unsatisfied need in the art for improved spreader apparatus designed to be used as a part of dryer/cooler inlet deck arrangements in order to provide essentially uniform spreading of pellets or like products across the entirety of an inlet deck.
The present invention overcomes the problems outlined above and provides spreader apparatus for use in inlet decks and the like. Broadly speaking, in a preferred embodiment, the spreader apparatus includes a plurality of elongated delivery tubes with outlet ends above an inlet deck, with a drive assembly coupled with the delivery tubes so as to successively move the tubes relative to the deck in order that essentially the entire product-receiving area of the deck is traversed by the delivery tube ends. A distributor is located above the delivery tubes for delivery of quantities of pellets or the like to each of the tubes. In this fashion, the pellets may be evenly spread through appropriate correlation of the volume of pellets delivered to the tubes and the rate of movement thereof over the inlet deck. Alternately, the spreader includes an annular, multiple-pocket tray together with a shiftable spout located above the tray for successive delivery of pellets to the tray pockets. A series of delivery ducts are located below the annular tray and are in communication with the pockets thereof. The delivery ducts deliver product to a conveyor belt or like device.
In preferred forms, where use is made of the delivery tubes, they are arranged in side-by-side relationship and are connected to form a tube array which extends substantially across the width of the inlet deck. Each of the delivery tubes includes a pair of telescopically interfitted upper and lower sections, with a pivotally coupled delivery shoe secured to the bottom ends of the lower tube sections. The upper tube sections are pivotally connected to and supported by the distributor, which advantageously includes a circular, multiple-pocket tray and a rotating spout to successively deliver product to each tray pocket. A ducting assembly is provided between the tray and the upper ends of the delivery tubes. The preferred drive assembly includes a drive cable arrangement which can be moved fore and aft in order to correspondingly move the drive delivery tube array along the length of the inlet deck. An alternate distributor includes an elongated trough positioned above the upper ends of the delivery tubes, together with an oscillating spout which fills the trough during operation.